In general substantive dyes or oxidation dyes are used for coloring keratinic fibers. Although intense colors with good fastness properties can be obtained with oxidation dyes, the development of the color generally takes place under the influence of oxidizing agents such as, for example, H2O2, which in some cases may result in damage to the fiber. Furthermore, some oxidation dye precursors, or certain mixtures of oxidation dye precursors, may have a sensitizing effect on people with sensitive skin. Substantive dyes are applied under gentler conditions. The disadvantage of these dyes, however, lies in the fact that the colors often have inadequate fastness properties, in particular with regard to hair washing, but also in respect of external influences, such as sunlight, or reactive environmental chemicals, such as swimming pool water. Substantive dyes are also used for shading oxidative colors.
Achieving a uniform coloring of frequently pretreated hair, such as bleached or permanently waved hair where the fibers have very differing degrees of pre-damage in the various lengths or variously treated areas, represents a particular challenge in terms of coloring hair with substantive dyes. For example, during the coloring process itself, a coloring agent can produce an uneven coloring on differently pre-damaged hair, while repeated hair washing can also cause the dyes to be washed out of the different areas of the hair to varying degrees, resulting in an inconsistent and hence undesirable color result.
In another example, for extreme lightening of dark hair, not only hydrogen peroxide alone but a combination of hydrogen peroxide and persulfates (e.g. ammonium persulfate, potassium persulfate and/or sodium persulfate) is used. Thus, if dark hair is to be significantly lightened in a single step and colored in a bright shade at the same time, the use of a mixture of hydrogen peroxide, persulfates and a substantive dye is advantageous. Although many intensely coloring substantive dyes are used, a very limited choice of dyes is available that can withstand the strong oxidative conditions created by mixing the aforementioned oxidizing agents without breaking down. In addition, the oxidation-stable dyes may have serious disadvantages in terms of their other fastness properties.
Therefore, for the simultaneous coloring and extreme lightening of hair there is a need for dyes having high stability with respect to strong oxidizing agents. Even under these extreme application conditions, these dyes should not lose their positive fastness and coloring properties.
Accordingly, an object of the present specification is to provide coloring agents for keratinic fibers, in particular human hair, having novel substantive dyes, which in terms of color depth and fastness properties (in particular light fastness, rubbing fastness, wash fastness, perspiration fastness, and cold wave fastness), have good application properties. It is also particularly desirable to provide coloring agents having a good equalizing capacity. In cases where they are used at the same time as oxidation dyes and/or oxidizing agents, the substantive dyes may have adequate stability in respect of hydrogen peroxide and other oxidizing agents and may not lose their positive fastness and coloring properties. In addition, the colors obtained should be as bright and intense as possible.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.